Drain valves are used in lavatories in order to release the water contained therein. A conventional drain valve comprises a drain hole which is a circular hole and a plug removably received in the drain hole. To control the release of the plug, a lift rod is connected with the plug and a control bar operates the lift rod. As disclosed in U.S. Pat. No. 3,453,667, the control bar can be forced down to lift the plug out of the drain hole. When using the drain valve, its normal position is in lower or downward position for containing water in the bowl in which the valve is installed. Due to gravity, the normal position of the control bar is in the lower condition. However this is contrary to the requirement of the plug. For a conventional drain plug, the plug upwardly protrudes from the drain hole. This is inconvenient for the uses when he used the water contained in the lavatory or cleans the lavatory. It is also difficult to clean the drain hole because of the obstacle of the plug. There is no filter formed in the drain hole, so that it is possible to drain waste through the drain hole to a drain pipe.